Recent developments of electromagnetic shielding sheets for wireless power transmission have been dominantly made for the purpose of achieving high efficiency and thinness. In other words, a magnetic material is used in an information technology (IT) component module for wireless power transmission, and owing to the use of such a magnetic material, an effort to enhance a function and performance of transmission efficiency (that is, wireless power transmission efficiency) has continued to minimize an electromagnetic energy loss by using an electromagnetic shielding material (that is, a magnetic substance) due to the use of such a magnetic material in addition to a practice of relying on only a coil design.
In terms of a shielding material configured with a magnetic substance, a shielding material capable of satisfying a function of wireless power transmission is necessary, and such a shielding material has a limitation in compatibility due to a diversification of standard methods for wireless power transmission. Typical examples of such standard methods for wireless power transmission include a wireless power consortium (WPC) method, an alliance for wireless power (A4WP) method, and a power matters alliance (PMA) method, and the standard methods are technically classified into magnetic induction methods and magnetic resonance methods.
A thin-film type metallic alloy which is implemented with a typical applicable magnetic material is attracting attention as such a shielding material, but excessively high permeability, which is realized by such a thin-film type metallic alloy, adversely affects impedance matching with an electromagnetic coil, and thus it is necessary to adjust permeability thereof.
Specifically, when a process, such as a cracking process, is performed on a thin-film type metallic alloy to adjust such permeability, burrs or fragments occur on the thin-film type metallic alloy itself, and thus damage to a surface or appearance thereof occurs, thereby causing a problem in which reliability is significantly degraded in an external hazardous environment due to the penetration of salt water and the like.